announcements 10/26/11
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Announcements 10/26/11. Prayer Slinkies: Please turn-in, and cross your name off of the sign out list. Exam 2 starts tomorrow, goes through Tuesday evening Covers through tonight’s HW (HW 24) Like last time, no notes allowed, but I give you equations - PowerPoint PPT PresentationTRANSCRIPT
Announcements 10/26/11 Prayer Slinkies: Please turn-in, and cross your name off of
the sign out list. Exam 2 starts tomorrow, goes through Tuesday
eveninga. Covers through tonight’s HW (HW 24)b. Like last time, no notes allowed, but I give you
equations Comment from Chris: when turning in multiple
assignments, staple them separately. Found a white sweater after review session last night.
Overboard
Reading Quiz Which of the following scientists did not attempt
to make a measurement of the speed of light?a. Einsteinb. Fizeauc. Galileod. Roemere. Michelson (OK, this is not the answer, but I felt
his name should be included on the list even though he wasn’t mentioned in today’s reading, because he performed the “canonical experiment”)
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How did they all attempt to measure it?
xkcd
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The wave nature of light
What is “waving”?http://stokes.byu.edu/emwave_flash.html
Medium?
Polarization: quick definition
Reading Quiz
A beam of light passes through a hole of diameter d in a metal plate. Under what condition are we allowed to ignore the diffraction or “spreading” of the light? (This is called the ray approximation.)
a. When λ << db. When λ ≈ dc. When λ >> d
lambda = d/10
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Next three slides: image credit to Dr. Durfee
lambda = d/4
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lambda = d
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Index of Refraction
Book table
v = c/n
Index of Refraction
Song: Roy G. Biv (start at 0:30)http://www.youtube.com/watch?v=Gf33ueRXMzQ
Image: http://en.wikipedia.org/wiki/Dispersion_(optics)
red
Different wavelengths have different speeds!
Different wave-lengths (k values) have different speeds!
v = f
Dispersion! greenblue( going into material)
inside = vacuum/n
Thought question
Which color of light travels fastest in glass?
a. Redb. Greenc. Blued. Same
Absorption “Lorentz oscillator model”
From Peatross & Ware, textbook for Phys 471
absorption
index of refraction
increasing frequency(decreasing )
“anomalous” index of refraction
Why is blue light slower through glass than red light? It’s closer to an absorption region
Index of Refraction Light ray at boundary
1
2
fast light(smaller n)
slow light(larger n)
Snell’s Law
n1sin1 = n2sin2
1
2
fast light(smaller n)
slow light(larger n)
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Law of Reflection
refl. = 1
1
2
fast light(smaller n)
slow light(larger n)
refl.
Reflections occur off of any boundary, not just “mirrors”
When will you have no reflection?
Fresnel Coefficients / Fresnel Equations
2 1 1 2
1 2 1 2
v v n nrv v n n
2 1
1 2 1 2
2 2v ntv v n n
If near perpendicular (1-D problem)
2R r 2
1T r
For arbitrary angle (these eqns not needed for HW/exam)
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1 1 2 2.
1 1 2 2
cos cos
cos coss polarn n
rn n
1 2 2 1.
1 2 2 1
cos cos
cos cosp polarn n
rn n
1 1.
1 1 2 2
2 cos
cos coss polarn
tn n
1 1.
1 2 2 1
2 cos
cos cosp polarn
tn n
Look familiar??
Thought question
I send white light into a prism as shown below (n>1). Will the red part of the “rainbow” be on the top or the bottom of the outgoing fan of light?
a. topb. bottom
top
bottom
Demos
Reflection/refraction using water-soluble oil
“Blackboard optics”